The invention relates to a bending frame for extending the travel of an actuator for a mechanically actuated component, and in particular for a proportional valve for fuel supply in an orbital propulsion system.
In order to mechanically actuate components, such as valves, it is common to use actuators that convert electrical signals into mechanical motion and actuate the component with this motion. Often, piezoelectric actuators or magnetostrictive actuators are used for this purpose. These have a disadvantage in often not having sufficient travel to actuate a large number of components.
Devices for extending the travel of an actuator are known from the prior art. DE 196 43 180 A1 describes a piezoactive actuation device having a mechanical motion amplifier. The piezoactive elements of the actuation device are surrounded by a shell having semi-elliptical arms. Expansion of the piezoactive elements in the longitudinal direction displaces the semi-elliptical arms perpendicularly to this longitudinal direction.
With the device for amplifying motion according to DE 196 43 180 A1, it proves to be a disadvantage that the direction in which the travel is increased is different from the travel of the actuator, resulting in large dimensions for the device.
The invention therefore addresses the problem of increasing the travel of an actuator in a simple and efficient manner through a compact device.
The problem is solved by a bending frame according to embodiments of the invention.
The bending frame according to an embodiment of the invention serves to extend the travel of an actuator for a mechanically actuated component. Generally, the actuator is a part of the component. An “actuator” is understood here and, henceforth, to be a converter that converts electrical signals into mechanical motion. Preferably, the actuator is a piezoelectric actuator, or optionally even a magnetostrictive actuator. The bending frame can, in principle, be used for any mechanically actuated components, but is preferably used for a valve. The valve is, in particular, a proportional valve and/or a fuel valve. In one variant, the valve is a proportional valve for fuel supply, and in particular a proportional valve for fuel supply in an orbital propulsion system, i.e. in a rocket propulsion.
The bending frame comprises a plurality of bendable longitudinal struts, which are arranged about a longitudinal axis on which the travel of the actuator runs. The longitudinal struts each extend the direction of the longitudinal axis, wherein an application of force enacted by the actuator along the actuation path on the longitudinal struts causes same to bend in a direction perpendicular to the longitudinal axis. Respective cross struts extend out toward the longitudinal axis from each of the longitudinal struts, i.e., a cross strut is provided for each of the longitudinal struts and each cross strut extends from the respective longitudinal strut. A first end of a respective cross strut is articulated to a respective longitudinal strut, and a second end of the respective cross strut opposite to the first end is provided in order to transmit a force to the mechanically actuated component in the direction of the longitudinal axis for the purpose of actuation thereof. In the bending frame according to an embodiment of the invention, the longitudinal struts and the cross struts interact with one another such that bending of the longitudinal struts causes the second ends of the cross struts to vary in the direction of the longitudinal axis due to the articulation of the first ends of the cross struts at the longitudinal struts, whereby the travel for mechanically actuating the component is extended.
The bending frame has an advantage in that a dual leverage redirection is achieved via the bendable longitudinal struts and the cross struts articulated thereto, so that the travel of the actuator in the direction of the longitudinal axis is increased and a compact device for motion amplification is provided by the bending frame.
In a preferred embodiment, the longitudinal struts of the bending frame each comprise two sub-struts, which are articulated at a connection point to one another. A particularly simple articulation is achieved in one variant of the invention by articulating the two sub-struts to one another the connection point via a film hinge. Preferably, the two sub-struts are of equal length. In particular when pressure is exerted on the bending frame by the actuator, the sub-struts are reinforced in a preferred variant, in order to prevent buckling thereof.
In another preferred embodiment, the cross struts extending out from each of the longitudinal struts are articulated with the first end thereof to the respective longitudinal strut via a film hinge, or to the position of the connection point. The film hinge is preferably the film hinge via which optionally also the two sub-struts of the respective longitudinal strut are interconnected.
In another preferred embodiment, the cross struts are interconnected at the second ends thereof, via a shared holding section, wherein the component is mechanically actuated via displacement of the holding section. This provides favorable force transmission for the mechanically actuated component.
In another preferred variant of the bending frame according to the invention, as seen in the direction of the longitudinal axis, all of the longitudinal struts have the same distance from the longitudinal axis, and the angles between adjacent longitudinal struts as measured from the longitudinal axis are of equal magnitude. Due to the design of the bending frame, these angles correspond to the angles between adjacent cross struts. The bending frame is thus endowed with a rotationally symmetrical structure. Such a bending frame is particularly suitable for adjusting cylindrical mechanically actuated components.
In another variant, the longitudinal struts are connected to one another at one of the ends thereof via a cross member running substantially perpendicularly to the longitudinal direction, wherein the longitudinal struts preferably are also connected to one another at the other ends thereof via a (different) cross member running substantially perpendicularly to the longitudinal direction. This makes it possible to very favorably apply force to the bending frame via these cross members. Preferably, each of the cross members is a ring that extends perpendicularly to the longitudinal axis and encircles the longitudinal axis, wherein the center point of the ring preferably lies on the longitudinal axis.
Depending on the configuration of the bending frame, the number of the longitudinal struts may be variously selected. However, at least two longitudinal struts must be provided. In a particularly preferred embodiment, the bending frame comprises four or more longitudinal struts.
In another variant, the bending frame is configured such that that the longitudinal struts bend towards the longitudinal axis along the actuation path when force is applied by the actuator. Optionally, there is also the possibility that the bending takes place away from the longitudinal axis.
The bending frame according to the invention is, in a preferred variant, an integrally-formed component that can be manufactured in a simple manner with a suitable production method. Preferably, the bending frame is made of metal or plastic.
In another variant, the bending frame is configured so that the travel is extended via application of pressure by the actuator onto the bending frame. Nonetheless, the bending frame may also be configured so that the travel is extended via application of traction by the actuator onto the bending frame.
As already mentioned above, the bending frame may be provided for a variety of types of actuators in order to extend the travel. Preferably, the actuator is a piezoelectric actuator, and in particular a piezoelectric ring actuator or a magnetostrictive actuator.
In addition to the bending frame described above, the invention further relates to a mechanically actuated component that comprises an actuator and the bending frame according to the invention or one or more preferred variants of the bending frame according to the invention. The bending frame then extends the travel of the actuator in order to actuate the mechanically actuated component.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.